Wei Yang, Huabiao Zhao, Baiqing Xu, Jiu-le Li, Weicai Wang, Guangjian Wu, Zhongyang Wang, T. Yao
Abstract. Exploring the snow depth on Mount Everest, one of the most inaccessible places on our planet, has long been a topic of interest. Previously reported snow depths have been inconsistent and have large uncertainties. Here, we report the ground-penetrating radar survey of snow depth along the north slope of Mount Everest in May 2022. Our radar measurements display a gradual increasing transition of snow depth along the north slope, and the mean depth estimates at the summit are 9.5±1.2 m. This updated snow depth on Mount Everest is much deeper than previously reported values (0.9–3.5 m).
{"title":"Brief communication: How deep is the snow on Mount Everest?","authors":"Wei Yang, Huabiao Zhao, Baiqing Xu, Jiu-le Li, Weicai Wang, Guangjian Wu, Zhongyang Wang, T. Yao","doi":"10.5194/tc-17-2625-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2625-2023","url":null,"abstract":"Abstract. Exploring the snow depth on Mount Everest, one of the most inaccessible places on our planet, has long been a\u0000topic of interest. Previously\u0000reported snow depths have been inconsistent and have large uncertainties.\u0000Here, we report the ground-penetrating radar survey of snow depth along the\u0000north slope of Mount Everest in May 2022. Our radar measurements display\u0000a gradual increasing transition of snow depth along the north slope, and the\u0000mean depth estimates at the summit are 9.5±1.2 m. This updated snow\u0000depth on Mount Everest is much deeper than previously reported values\u0000(0.9–3.5 m).\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45562284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The supraglacial drainage system of the Greenland Ice Sheet, in combination with surface melt rate, controls the rate of water flow into moulins, a major driver of subglacial water pressure. We apply the Subaerial Drainage System (SaDS) model, a physically based surface meltwater flow model, to a ∼20×27km2 catchment on the southwestern Greenland Ice Sheet for 4 years of melt forcing (2011, 2012, 2015, and 2016) to (1) examine the relationship between surface melt rate and the rate, diurnal amplitude, and timing of surface inputs to moulins; (2) compare SaDS to contemporary models; and (3) present a framework for selecting appropriate supraglacial drainage models for different modelling objectives. We find that variations in the rate and timing of modelled moulin inputs related to the development of supraglacial channels are relatively more important in years with low melt volumes than years with high melt volumes. We suggest that a process-resolving supraglacial hydrology model (e.g., SaDS) should be considered when modelling outcomes are sensitive to subdiurnal and long-term seasonal changes in the rate of discharge into moulins.
{"title":"The impact of surface melt rate and catchment characteristics on Greenland Ice Sheet moulin inputs","authors":"T. Hill, C. Dow","doi":"10.5194/tc-17-2607-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2607-2023","url":null,"abstract":"Abstract. The supraglacial drainage system of the Greenland Ice Sheet, in combination with surface melt rate, controls the rate of water flow into moulins, a major driver of subglacial water pressure. We apply the Subaerial Drainage System (SaDS) model, a physically based surface meltwater flow model, to a ∼20×27km2 catchment on the southwestern Greenland Ice Sheet for 4 years of melt forcing (2011, 2012, 2015, and 2016) to (1) examine the relationship between surface melt rate and the rate, diurnal amplitude, and timing of surface inputs to moulins; (2) compare SaDS to contemporary models; and (3) present a framework for selecting appropriate supraglacial drainage models for different modelling objectives. We find that variations in the rate and timing of modelled moulin inputs related to the development of supraglacial channels are relatively more important in years with low melt volumes than years with high melt volumes. We suggest that a process-resolving supraglacial hydrology model (e.g., SaDS) should be considered when modelling outcomes are sensitive to subdiurnal and long-term seasonal changes in the rate of discharge into moulins.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70704437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Mosbeux, L. Padman, E. Klein, P. Bromirski, H. Fricker
Abstract. Antarctica's ice shelves resist the flow of grounded ice towards the ocean through “buttressing” arising from their contact with ice rises, rumples, and lateral margins. Ice shelf thinning and retreat reduce buttressing, leading to increased delivery of mass to the ocean that adds to global sea level. Ice shelf response to large annual cycles in atmospheric and oceanic processes provides opportunities to study the dynamics of both ice shelves and the buttressed grounded ice. Here, we explore whether seasonal variability of sea surface height (SSH) can explain observed seasonal variability of ice velocity. We investigate this hypothesis using several time series of ice velocity from the Ross Ice Shelf (RIS), satellite-based estimates of SSH seaward of the RIS front, ocean models of SSH under and near RIS, and a viscous ice sheet model. The observed annual changes in RIS velocity are of the order of 1–10 m a−1 (roughly 1 % of mean flow). The ice sheet model, forced by the observed and modelled range of SSH of about 10 cm, reproduces the observed velocity changes when sufficiently large basal drag changes near the grounding line are parameterised. The model response is dominated by grounding line migration but with a significant contribution from SSH-induced tilt of the ice shelf. We expect that climate-driven changes in the seasonal cycles of winds and upper-ocean summer warming will modify the seasonal response of ice shelves to SSH and that nonlinear responses of the ice sheet will affect the longer trend in ice sheet response and its potential sea-level rise contribution.
摘要南极洲的冰架通过与冰隆、褶皱和侧缘接触产生的“支撑”来抵抗搁浅的冰向海洋的流动。冰架变薄和退缩减少了吸引力，导致向海洋输送的质量增加，从而增加了全球海平面。冰架对大气和海洋过程中大的年周期的响应为研究冰架和支撑搁浅冰的动力学提供了机会。在这里，我们探讨了海面高度的季节变化是否可以解释观测到的冰速的季节变化。我们使用来自罗斯冰架（RIS）的几个冰速时间序列、基于卫星的RIS锋面SSH向海估计、RIS下和附近的SH海洋模型以及粘性冰盖模型来研究这一假设。观测到的RIS速度的年变化约为1-10 m a−1（大约1 % 曼流）。冰盖模型，由观测和建模的SSH范围约为10 cm再现了当接地线附近足够大的基础阻力变化被参数化时观察到的速度变化。模型响应主要由接地线迁移引起，但SSH引起的冰架倾斜对模型响应有显著影响。我们预计，气候驱动的风的季节性周期变化和上层海洋夏季变暖将改变冰架对SSH的季节性响应，而冰盖的非线性响应将影响冰盖响应的长期趋势及其潜在的海平面上升贡献。
{"title":"Seasonal variability in Antarctic ice shelf velocities forced by sea surface height variations","authors":"C. Mosbeux, L. Padman, E. Klein, P. Bromirski, H. Fricker","doi":"10.5194/tc-17-2585-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2585-2023","url":null,"abstract":"Abstract. Antarctica's ice shelves resist the flow of grounded ice towards\u0000the ocean through “buttressing” arising from their contact with ice rises,\u0000rumples, and lateral margins. Ice shelf thinning and retreat reduce\u0000buttressing, leading to increased delivery of mass to the ocean that adds to\u0000global sea level. Ice shelf response to large annual cycles in atmospheric\u0000and oceanic processes provides opportunities to study the dynamics of both\u0000ice shelves and the buttressed grounded ice. Here, we explore whether\u0000seasonal variability of sea surface height (SSH) can explain observed\u0000seasonal variability of ice velocity. We investigate this hypothesis using\u0000several time series of ice velocity from the Ross Ice Shelf (RIS),\u0000satellite-based estimates of SSH seaward of the RIS front, ocean models of\u0000SSH under and near RIS, and a viscous ice sheet model. The observed annual\u0000changes in RIS velocity are of the order of 1–10 m a−1 (roughly 1 % of\u0000mean flow). The ice sheet model, forced by the observed and modelled range\u0000of SSH of about 10 cm, reproduces the observed velocity changes when\u0000sufficiently large basal drag changes near the grounding line are\u0000parameterised. The model response is dominated by grounding line migration\u0000but with a significant contribution from SSH-induced tilt of the ice shelf.\u0000We expect that climate-driven changes in the seasonal cycles of winds and\u0000upper-ocean summer warming will modify the seasonal response of ice shelves\u0000to SSH and that nonlinear responses of the ice sheet will affect the longer\u0000trend in ice sheet response and its potential sea-level rise contribution.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49107796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. With progressing global warming, snowfall in Antarctica is expected to increase, which could counteract or even temporarily overcompensate increased ice-sheet mass losses caused by increased ice discharge and melting. For sea-level projections it is therefore vital to understand the processes determining snowfall changes in Antarctica. Here we revisit the relationship between Antarctic temperature changes and precipitation changes, identifying and explaining regional differences and deviations from the theoretical approach based on the Clausius–Clapeyron relationship. Analysing the latest estimates from global (CMIP6, Coupled Model Intercomparison Project Phase 6) and regional (RACMO2.3) model projections, we find an average increase of 5.5 % in annual precipitation over Antarctica per degree of warming, with a minimum sensitivity of 2 % K−1 near Siple Coast and a maximum sensitivity of > 10 % K−1 at the East Antarctic plateau region. This large range can be explained by the prevailing climatic conditions, with local temperatures determining the Clausius–Clapeyron sensitivity that is counteracted in some regions by the prevalence of the coastal wind regime. We compare different approaches of deriving the sensitivity factor, which in some cases can lead to sensitivity changes of up to 7 percentage points for the same model. Importantly, local sensitivity factors are found to be strongly dependent on the warming level, suggesting that some ice-sheet models which base their precipitation estimates on parameterisations derived from these sensitivity factors might overestimate warming-induced snowfall changes, particularly in high-emission scenarios. This would have consequences for Antarctic sea-level projections for this century and beyond.
{"title":"Revisiting temperature sensitivity: how does Antarctic precipitation change with temperature?","authors":"Lena Nicola, D. Notz, R. Winkelmann","doi":"10.5194/tc-17-2563-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2563-2023","url":null,"abstract":"Abstract. With progressing global warming, snowfall in Antarctica is expected to increase, which could counteract or even temporarily overcompensate increased ice-sheet mass losses caused by increased ice discharge and melting. For sea-level projections it is therefore vital to understand the processes determining snowfall changes in Antarctica. Here we revisit the relationship between Antarctic temperature changes and precipitation changes, identifying and explaining regional differences and deviations from the theoretical approach based on the Clausius–Clapeyron relationship. Analysing the latest estimates from global (CMIP6, Coupled Model Intercomparison Project Phase 6) and regional (RACMO2.3) model projections, we find an average increase of 5.5 % in annual precipitation over Antarctica per degree of warming, with a minimum sensitivity of 2 % K−1 near Siple Coast and a maximum sensitivity of > 10 % K−1 at the East Antarctic plateau region. This large range can be explained by the prevailing climatic conditions, with local temperatures determining the Clausius–Clapeyron sensitivity that is counteracted in some regions by the prevalence of the coastal wind regime. We compare different approaches of deriving the sensitivity factor, which in some cases can lead to sensitivity changes of up to 7 percentage points for the same model.\u0000Importantly, local sensitivity factors are found to be strongly dependent on the warming level, suggesting that some ice-sheet models which base their precipitation estimates on parameterisations derived from these sensitivity factors might overestimate warming-induced snowfall changes, particularly in high-emission scenarios. This would have consequences for Antarctic sea-level projections for this century and beyond.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47400829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Obase, A. Abe‐Ouchi, F. Saito, S. Tsutaki, S. Fujita, K. Kawamura, H. Motoyama
Abstract. The recovery of a new Antarctic ice core spanning the past ∼ 1.5 million years will advance our understanding of climate system dynamics during the Quaternary. Recently, glaciological field surveys have been conducted to select the most suitable core location near Dome Fuji (DF), Antarctica. Specifically, ground-based radar-echo soundings have been used to acquire highly detailed images of bedrock topography and internal ice layers. In this study, we use a one-dimensional (1-D) ice-flow model to compute the temporal evolutions of age and temperature, in which the ice flow is linked with not only transient climate forcing associated with past glacial–interglacial cycles but also transient basal melting diagnosed along the evolving temperature profile. We investigated the influence of ice thickness, accumulation rate, and geothermal heat flux on the age and temperature profiles. The model was constrained by the observed temperature and age profiles reconstructed from the DF ice-core analysis. The results of sensitivity experiments indicate that ice thickness is the most crucial parameter influencing the computed age of the ice because it is critical to the history of basal temperature and basal melting, which can eliminate old ice. The 1-D model was applied to a 54 km long transect in the vicinity of DF and compared with radargram data. We found that the basal age of the ice is mostly controlled by the local ice thickness, demonstrating the importance of high-spatial-resolution surveys of bedrock topography for selecting ice-core drilling sites.
{"title":"A one-dimensional temperature and age modeling study for selecting the drill site of the oldest ice core near Dome Fuji, Antarctica","authors":"T. Obase, A. Abe‐Ouchi, F. Saito, S. Tsutaki, S. Fujita, K. Kawamura, H. Motoyama","doi":"10.5194/tc-17-2543-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2543-2023","url":null,"abstract":"Abstract. The recovery of a new Antarctic ice core spanning the past\u0000∼ 1.5 million years will advance our understanding of climate\u0000system dynamics during the Quaternary. Recently, glaciological field surveys\u0000have been conducted to select the most suitable core location near Dome Fuji\u0000(DF), Antarctica. Specifically, ground-based radar-echo soundings have been\u0000used to acquire highly detailed images of bedrock topography and internal\u0000ice layers. In this study, we use a one-dimensional (1-D) ice-flow model to\u0000compute the temporal evolutions of age and temperature, in which the ice\u0000flow is linked with not only transient climate forcing associated with past\u0000glacial–interglacial cycles but also transient basal melting diagnosed\u0000along the evolving temperature profile. We investigated the influence of ice\u0000thickness, accumulation rate, and geothermal heat flux on the age and\u0000temperature profiles. The model was constrained by the observed temperature\u0000and age profiles reconstructed from the DF ice-core analysis. The results of\u0000sensitivity experiments indicate that ice thickness is the most crucial\u0000parameter influencing the computed age of the ice because it is critical to\u0000the history of basal temperature and basal melting, which can eliminate old\u0000ice. The 1-D model was applied to a 54 km long transect in the vicinity of\u0000DF and compared with radargram data. We found that the basal age of the ice\u0000is mostly controlled by the local ice thickness, demonstrating the\u0000importance of high-spatial-resolution surveys of bedrock topography for\u0000selecting ice-core drilling sites.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45393951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Following the 130 ± 5 × 106 m3 detachment of the Sedongpu Glacier, south-eastern Tibet, in October 2018, the Sedongpu Valley, which drains into the Yarlung Tsangpo (Brahmaputra) River, underwent rapid large-volume landscape changes. Between December 2018 and 2022 and in particular during summer 2021, an enormous volume of in total ∼ 335 ± 5 × 106 m3 was eroded from the former glacier bed, forming a new canyon of up to 300 m depth, 1 km width, and almost 4 km length. The 2021 erosion peak happened through massive but still gradual retrogressive erosion into the former glacier bed. Several rock–ice avalanches of in total ∼ 150 ± 5 × 106 m3 added to the total rock, sediment, and ice volume of over 600 × 106 m3 (0.6 km3) that has been exported from the basin since around 2017. The recent erosion volumes at Sedongpu are by order of magnitude equivalent to the average annual denudation volume of the entire Brahmaputra basin upstream of the location where the river leaves the Himalayas. This high-magnitude low-frequency event illustrates the potential for rapid post-glacial landscape evolution and associated hazards that has rarely been observed and considered at such high intensity so far.
{"title":"Brief communication: Rapid ∼ 335 × 106 m3 bed erosion after detachment of the Sedongpu Glacier (Tibet)","authors":"A. Kääb, L. Girod","doi":"10.5194/tc-17-2533-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2533-2023","url":null,"abstract":"Abstract. Following the 130 ± 5 × 106 m3 detachment of\u0000the Sedongpu Glacier, south-eastern Tibet, in October 2018, the Sedongpu\u0000Valley, which drains into the Yarlung Tsangpo (Brahmaputra) River, underwent\u0000rapid large-volume landscape changes. Between December 2018 and 2022 and in\u0000particular during summer 2021, an enormous volume of in total\u0000∼ 335 ± 5 × 106 m3 was eroded from the former\u0000glacier bed, forming a new canyon of up to 300 m depth, 1 km width, and\u0000almost 4 km length. The 2021 erosion peak happened through massive but still\u0000gradual retrogressive erosion into the former glacier bed. Several rock–ice\u0000avalanches of in total ∼ 150 ± 5 × 106 m3 added\u0000to the total rock, sediment, and ice volume of over 600 × 106 m3 (0.6 km3) that has been exported from the basin since around 2017. The recent\u0000erosion volumes at Sedongpu are by order of magnitude equivalent to the\u0000average annual denudation volume of the entire Brahmaputra basin upstream of\u0000the location where the river leaves the Himalayas. This high-magnitude\u0000low-frequency event illustrates the potential for rapid post-glacial landscape\u0000evolution and associated hazards that has rarely been observed and\u0000considered at such high intensity so far.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43217336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. We estimate the snow depth and snow freeboard of Antarctic sea ice using a comprehensive retrieval method (referred to as CryoSat-2 Waveform Fitting for Antarctic sea ice, or CS2WFA) consisting of a physical waveform model and a waveform-fitting process that fits modeled waveforms to CryoSat-2 data. These snow depth and snow freeboard estimates are combined with snow, sea ice, and sea water density values to calculate the sea ice thickness and volume over an 11+ year span between 2010 and 2021. We first compare our snow freeboard, snow depth, and sea ice thickness estimates to other altimetry- and ship-based observations and find good agreement overall in both along-track and monthly gridded comparisons. Some discrepancies exist in certain regions and seasons that are theorized to come from both sampling biases and the differing assumptions in the retrieval methods. We then present an 11+ year time series of sea ice thickness and volume both regionally and pan-Antarctic. This time series is used to uncover intra-decadal changes in the ice cover between 2010 and 2021, showing small, competing regional thickness changes of less than 0.5 cm yr−1 in magnitude. Finally, we place these thickness estimates in the context of a longer-term, snow freeboard-derived, laser–radar sea ice thickness time series that began with NASA's Ice, Cloud, and land Elevation Satellite (ICESat) and continues with ICESat-2 and contend that reconciling and validating this longer-term, multi-sensor time series will be important in better understanding changes in the Antarctic sea ice cover.
{"title":"A decade-plus of Antarctic sea ice thickness and volume estimates from CryoSat-2 using a physical model and waveform fitting","authors":"S. Fons, N. Kurtz, M. Bagnardi","doi":"10.5194/tc-17-2487-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2487-2023","url":null,"abstract":"Abstract. We estimate the snow depth and snow freeboard of Antarctic sea ice using a comprehensive retrieval method (referred to as CryoSat-2 Waveform Fitting for Antarctic sea ice, or CS2WFA) consisting of a physical waveform model and a waveform-fitting process that fits modeled waveforms to CryoSat-2 data.\u0000These snow depth and snow freeboard estimates are combined with snow, sea ice, and sea water density values to calculate the sea ice thickness and volume over an 11+ year span between 2010 and 2021. We first compare our snow freeboard, snow depth, and sea ice thickness estimates to other altimetry- and ship-based observations and find good agreement overall in both along-track and monthly gridded comparisons. Some discrepancies exist in certain regions and seasons that are theorized to come from both sampling biases and the differing assumptions in the retrieval methods. We then present an 11+ year time series of sea ice thickness and volume both regionally and pan-Antarctic. This time series is used to uncover intra-decadal changes in the ice cover between 2010 and 2021, showing small, competing regional thickness changes of less than 0.5 cm yr−1 in magnitude.\u0000Finally, we place these thickness estimates in the context of a longer-term, snow freeboard-derived, laser–radar sea ice thickness time series that began with NASA's Ice, Cloud, and land Elevation Satellite (ICESat) and continues with ICESat-2 and contend that reconciling and validating this longer-term, multi-sensor time series will be important in better understanding changes in the Antarctic sea ice cover.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45977421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xuemei Li, Xinyu Liu, Kaixin Zhao, Xu Zhang, Lan-hai Li
Abstract. The acceleration of climate warming has led to a faster solid–liquid water cycle and a decrease in solid water storage in cold regions of the Earth. Although snowfall is the most critical input for the cryosphere, the phenology of snowfall, or potential snowfall phenology (PSP), has not been thoroughly studied, and there is a lack of indicators for PSP. For this reason, we have proposed three innovative indicators, namely, the start of potential snowfall season (SPSS), the end of potential snowfall season (EPSS), and the length of potential snowfall season (LPSS), to characterize the PSP. We then explored the spatial–temporal variation in all three PSP indicators in the past, present, and future across the Chinese Tianshan mountainous region (CTMR) based on the observed daily air temperature from 26 meteorological stations during 1961–2017/2020 combined with data from 14 models from CMIP6 (Phase 6 of the Coupled Model Intercomparison Project) under four different scenarios (SSP126, SSP245, SSP370, and SSP585, where SSP represents Shared Socioeconomic Pathway) during 2021–2100. The study showed that the SPSS, EPSS, and LPSS indicators could accurately describe the PSP characteristics across the study area. In the past and present, the potential snowfall season started on 2 November, ended on 18 March, and lasted for about 4.5 months across the CTMR on average. During 1961–2017/2020, the rate of advancing the EPSS (−1.6 d per decade) was faster than that of postponing the SPSS (1.2 d per decade). It was also found that there was a significant delay in the starting time (2–13 d) and advancement in the ending time (1–13 d), respectively, resulting in a reduction of 3–26 d for the LPSS. The potential snowfall season started earlier, ended later, and lasted longer in the north and center compared with the south. Similarly, the SPSS, EPSS, and LPSS indicators are also expected to vary under the four emission scenarios during 2021–2100. Under the highest emission scenario, SSP585, the starting time is expected to be postponed by up to 41 d, while the ending time is expected to be advanced by up to 23 d across the study area. This change is expected to reduce the length of the potential snowfall season by up to 61 d (about 2 months), and the length of the potential snowfall season will only last 2.5 months in the 2100s under the SSP585 scenario. The length of the potential snowfall season in the west and southwest of the CTMR will be compressed by more days due to a more delayed starting time and an advanced ending time under all four scenarios. This suggests that, with constant snowfall intensity, annual total snowfall may decrease, including the amount and frequency, leading to a reduction in snow cover or mass, which will ultimately contribute to more rapid warming through the lower reflectivity to solar radiation. This research provides new insights into capturing the potential snowfall phenology in the alpine region and can be easily extend
{"title":"Change in the potential snowfall phenology: past, present, and future in the Chinese Tianshan mountainous region, Central Asia","authors":"Xuemei Li, Xinyu Liu, Kaixin Zhao, Xu Zhang, Lan-hai Li","doi":"10.5194/tc-17-2437-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2437-2023","url":null,"abstract":"Abstract. The acceleration of climate warming has led to a faster\u0000solid–liquid water cycle and a decrease in solid water storage in cold\u0000regions of the Earth. Although snowfall is the most critical input for the\u0000cryosphere, the phenology of snowfall, or potential snowfall phenology\u0000(PSP), has not been thoroughly studied, and there is a lack of indicators\u0000for PSP. For this reason, we have proposed three innovative indicators,\u0000namely, the start of potential snowfall season (SPSS), the end of potential\u0000snowfall season (EPSS), and the length of potential snowfall season (LPSS),\u0000to characterize the PSP. We then explored the spatial–temporal variation in\u0000all three PSP indicators in the past, present, and future across the Chinese\u0000Tianshan mountainous region (CTMR) based on the observed daily air\u0000temperature from 26 meteorological stations during 1961–2017/2020 combined\u0000with data from 14 models from CMIP6 (Phase 6 of the Coupled Model\u0000Intercomparison Project) under four different scenarios (SSP126, SSP245,\u0000SSP370, and SSP585, where SSP represents Shared Socioeconomic Pathway) during 2021–2100. The study showed that the SPSS, EPSS,\u0000and LPSS indicators could accurately describe the PSP characteristics across\u0000the study area. In the past and present, the potential snowfall season\u0000started on 2 November, ended on 18 March, and lasted for about\u00004.5 months across the CTMR on average. During 1961–2017/2020,\u0000the rate of advancing the EPSS (−1.6 d per decade) was faster than that of\u0000postponing the SPSS (1.2 d per decade). It was also found that there was a\u0000significant delay in the starting time (2–13 d) and advancement in the\u0000ending time (1–13 d), respectively, resulting in a reduction of 3–26 d\u0000for the LPSS. The potential snowfall season started earlier, ended later,\u0000and lasted longer in the north and center compared with the south. Similarly,\u0000the SPSS, EPSS, and LPSS indicators are also expected to vary under the four\u0000emission scenarios during 2021–2100. Under the highest emission scenario,\u0000SSP585, the starting time is expected to be postponed by up to 41 d,\u0000while the ending time is expected to be advanced by up to 23 d across the\u0000study area. This change is expected to reduce the length of the potential\u0000snowfall season by up to 61 d (about 2 months), and the length of the\u0000potential snowfall season will only last 2.5 months in the 2100s\u0000under the SSP585 scenario. The length of the potential snowfall season in\u0000the west and southwest of the CTMR will be compressed by more days due to a\u0000more delayed starting time and an advanced ending time under all four\u0000scenarios. This suggests that, with constant snowfall intensity, annual total\u0000snowfall may decrease, including the amount and frequency, leading to a\u0000reduction in snow cover or mass, which will ultimately contribute to more\u0000rapid warming through the lower reflectivity to solar radiation. This\u0000research provides new insights into capturing the potential snowfall\u0000phenology in the alpine region and can be easily extend","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44251123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Nilsson, E. V. van Dongen, M. Jakobsson, M. O’Regan, C. Stranne
Abstract. Using a conceptual model, we examine how hydraulically controlled exchange flows in silled fjords affect the relationship between the basal glacier melt and the features of warm intermediate Atlantic Water (AW) outside the fjords. We show that an exchange flow can be forced to transit into the hydraulic regime if the AW interface height decreases, the AW temperature increases, or the production of glacially modified water is boosted by subglacial discharge. In the hydraulic regime, the heat transport across the sill becomes a rate-limiting factor for the basal melt, which is suppressed. An interplay between processes near the ice–ocean boundary and the hydraulically controlled exchange flow determines the melt dynamics, and the sensitivity of the basal melt to changes in the AW temperature is reduced. The model results are discussed in relation to observations from the Petermann, Ryder, and 79∘ N glaciers in northern Greenland.
{"title":"Hydraulic suppression of basal glacier melt in sill fjords","authors":"J. Nilsson, E. V. van Dongen, M. Jakobsson, M. O’Regan, C. Stranne","doi":"10.5194/tc-17-2455-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2455-2023","url":null,"abstract":"Abstract. Using a conceptual model, we examine how hydraulically controlled exchange flows in silled fjords affect the relationship between the basal glacier melt and the features of warm intermediate Atlantic Water (AW) outside the fjords. We show that an exchange flow can be forced to transit into the hydraulic regime if the AW interface height decreases, the AW temperature increases, or the production of glacially modified water is boosted by subglacial discharge. In the hydraulic regime, the heat transport across the sill becomes a rate-limiting factor for the basal melt, which is suppressed. An interplay between processes near the ice–ocean boundary and the hydraulically controlled exchange flow determines the melt dynamics, and the sensitivity of the basal melt to changes in the AW temperature is reduced. The model results are discussed in relation to observations from the Petermann, Ryder, and 79∘ N glaciers in northern Greenland.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43375520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. McKenzie, Lauren E. Miller, Jacob S. Slawson, E. Mackie, Shujie Wang
Abstract. Topographic highs (“bumps”) across glaciated landscapes have the potential to temporarily slow ice sheet flow or, conversely, accelerate ice flow through subglacial strain heating and meltwater production. Isolated bumps of variable size across the deglaciated landscape of the Cordilleran Ice Sheet (CIS) of Washington State present an opportunity to study the influence of topographic highs on ice–bed interactions and ice flow organization. This work utilizes semi-automatic mapping techniques of subglacial bedforms to characterize the morphology of streamlined subglacial bedforms including elongation, surface relief, and orientation, all of which provide insight into subglacial processes during post-Last Glacial Maximum deglaciation. We identify a bump-size threshold of several cubic kilometers – around 4.5 km3 – in which bumps larger than this size will consistently and significantly disrupt both ice flow organization and subglacial sedimentary processes, which are fundamental to the genesis of streamlined subglacial bedforms. Additionally, sedimentary processes are persistent and well developed downstream of bumps, as reflected by enhanced bedform elongation and reduced surface relief, likely due to increased availability and production of subglacial sediment and meltwater. While isolated topography plays a role in disrupting ice flow, larger bumps have a greater disruption to ice flow organization, while bumps below the identified threshold seem to have little effect on ice and subglacial processes. The variable influence of isolated topographic bumps on ice flow of the CIS has significant implications for outlet glaciers of the Greenland Ice Sheet (GrIS) due to similarities in regional topography, where local bumps are largely unresolved.
{"title":"Differential impact of isolated topographic bumps on ice sheet flow and subglacial processes","authors":"M. McKenzie, Lauren E. Miller, Jacob S. Slawson, E. Mackie, Shujie Wang","doi":"10.5194/tc-17-2477-2023","DOIUrl":"https://doi.org/10.5194/tc-17-2477-2023","url":null,"abstract":"Abstract. Topographic highs (“bumps”) across glaciated landscapes have the\u0000potential to temporarily slow ice sheet flow or, conversely, accelerate ice\u0000flow through subglacial strain heating and meltwater production. Isolated\u0000bumps of variable size across the deglaciated landscape of the Cordilleran\u0000Ice Sheet (CIS) of Washington State present an opportunity to study the\u0000influence of topographic highs on ice–bed interactions and ice flow\u0000organization. This work utilizes semi-automatic mapping techniques of\u0000subglacial bedforms to characterize the morphology of streamlined subglacial\u0000bedforms including elongation, surface relief, and orientation, all of which\u0000provide insight into subglacial processes during post-Last Glacial Maximum\u0000deglaciation. We identify a bump-size threshold of several cubic kilometers\u0000– around 4.5 km3 – in which bumps larger than this size will\u0000consistently and significantly disrupt both ice flow organization and\u0000subglacial sedimentary processes, which are fundamental to the genesis of\u0000streamlined subglacial bedforms. Additionally, sedimentary processes are\u0000persistent and well developed downstream of bumps, as reflected by enhanced\u0000bedform elongation and reduced surface relief, likely due to increased\u0000availability and production of subglacial sediment and meltwater. While\u0000isolated topography plays a role in disrupting ice flow, larger bumps have a\u0000greater disruption to ice flow organization, while bumps below the\u0000identified threshold seem to have little effect on ice and subglacial\u0000processes. The variable influence of isolated topographic bumps on ice flow\u0000of the CIS has significant implications for outlet glaciers of the Greenland\u0000Ice Sheet (GrIS) due to similarities in regional topography, where local\u0000bumps are largely unresolved.\u0000","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":5.2,"publicationDate":"2023-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43601930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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